A solenoid valve driving a plunger is provided with an electromagnetic coil encapsulated in a yoke. A longitudinal hole is formed at the center of the electromagnetic coil and a cylindrical plunger guide is mounted in the longitudinal hole. Further, a pole core is fixedly fitted to the upper portion of the plunger guide and the plunger moving relative to the pole core is abrasively inserted into the plunger guide. Also, a bleed hole communicating with water supply source and a pilot hole communicating with the secondary side of water supply are installed to a diaphragm provided to a diaphragm valve.
According to such a structure, the outer shell of a solenoid is formed by the yoke, a lower end plate thereof and a pole core fixing plate to which the pole core is fixed. Further, the plunger is operated movably to and from a through hole at a yoke lower end plate by receiving a magnetic sucking action caused by the electromagnetic force generated by conducting electricity to the electromagnetic coil. Thereby, the diaphragm valve is opened and closed by opening and closing the pilot hole of the diaphragm in accordance with the movement of the plunger.
The field of use of a solenoid valve for water supply control has been diversified in recent years and, for example, the valve is adopted in water related devices in general life such as an automatic cock, a privates washing device and the like. Hence, reduction in cost and further downsizing have been desired by the market.
However, there is a limitation in dealing with the downsizing according to the above-described structure and there are various hazards in achieving the further downsizing thereof.
That is, in downsizing a solenoid valve, plunger stroke or diaphragm area may be reduced in order to simply downsize it. However, it is known that handling performance of a solenoid valve for water supply control is deteriorated unless it is used normally under a hydraulic pressure of 0.5 through 10 kg/cm.sup.2 and a flow rate of approximately 20 liter per minute is ensured even under aminimum hydraulic pressure of use.
Therefore, there is a limitation in decreasing the plunger stroke or the diaphragm area. On the other hand, if other constitutions are to be reconstructed, deterioration in the function, or deterioration in the water proof function may be caused. Therefore, it is extremely difficult to achieve downsizing exceeding the current state while maintaining the function.
It is an object of the present invention to provide a solenoid and a solenoid valve capable of solving the above-described problem.